Apparatus for extruding sheets of material are known in the art. For example, Chiverton U.S. Pat. No. 2,052,695 discloses a device for producing films or foils from cellulose acetate. Wickham U.S. Pat. No. 1,924,010 discloses a device for casting double films of materials such as cellulose acetate. Hayward, U.S. Pat. No. 5,256,357 discloses an apparatus for forming non-gelatin, polymeric films of two or more layers. The films are formed by a die having fixed, non-adjustable extrusion slots.
Apparatus for extruding gelatin sheets are also known in the art. Ericson, U.S. Pat. No. 2,815,533 discloses a gelatin encapsulating spreader box which uses a single adjustable doctor blade to vary the thickness of a gelatin layer. Scherer, U.S. Pat. No. 2,339,114 discloses a spreader box for forming a gelatin layer which uses a single adjustable doctor blade to vary the thickness of a gelatin layer.
Capsules of more than one layer are also known. Scherer, U.S. Pat. No. 2,379,831 discloses a gelatin capsule which can include multiple layers. However, the substance forming the additional layer is disclosed as being other than gelatin, because a fill material in the capsule is incompatible with gelatin. Also, the capsules are formed by nozzle extrusion. Kikuchi, U.S. Pat. No. 5,330,835 and Suzuki, U.S. Pat. No. 5,362,564 also disclose a gelatin capsule which can include multiple layers. The substance forming the additional layer is disclosed as being other than gelatin, because a fill material in the capsule is incompatible with gelatin. Also, the capsules are formed by nozzle extrusion. Mizuno, U.S. Pat. No. 4,350,679 discloses a gelatin capsule coated with a wax, such as carnauba wax. The use of wax instead of an additional gelatin layer is taught as preventing problems associated with having an external gelatin layer.
It would be desirable to have softgel capsules which can exhibit different properties such as the degree of permeability, rate of dissolution, mouth feel, taste, and color. These different properties can be provided by producing capsules having more than one layer of gelatin. It also would be desirable to produce a softgel capsule of more than one color, for example, a light color such as yellow and a dark color such as blue, in which the dark color did not rub off on the light color when a number of softgels are in contact with each. Application of a clear gelatin layer over the colored gelatin layer can eliminate such color transfer problems.
Accordingly, it would be desirable to provide a gelatin spreader box that allows for the extrusion of two separate gelatin layers which can vary in thickness and in other properties such as the degree of permeability, rate of dissolution, mouth feel, taste and color, and to provide multiple layer softgels.